California High-Speed Rail construction of the Fresno River Viaduct in the Central Valley. Aerial structures similar to these might be built in Fairfield County for Amtrak trains, roughly following Interstate 95. less

California High-Speed Rail construction of the Fresno River Viaduct in the Central Valley. Aerial structures similar to these might be built in Fairfield County for Amtrak trains, roughly following Interstate ... more

Photo: California High-Speed Rail Authority / Contributed Photo

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Contractors for the California High-Speed Rail Authority erect a viaduct for elevated high-speed rail tracks near Cedar and North avenues and State Route 99 in Fresno, California, in this Dec. 6, 2016 photo. Aerial structures similar to these might be built in Fairfield County for Amtrak trains, roughly following Interstate 95. less

Contractors for the California High-Speed Rail Authority erect a viaduct for elevated high-speed rail tracks near Cedar and North avenues and State Route 99 in Fresno, California, in this Dec. 6, 2016 photo. ... more

Photo: Tim Sheehan / Contributed Photo

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New rail lines: In the air, not out of sight

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NORWALK — Under the Federal Rail Administration’s proposed new high-speed rail plan for the Northeast Corridor, trains would run through Fairfield County partly along “aerial structures.”

A new, two-track infrastructure would continue from Westchester County, N.Y., through coastal Fairfield County. The new line would parallel Interstate 95 — “typically on embankment or aerial structure” — through Greenwich, Stamford and Norwalk, and merge with the existing railbeds west of the Greens Farms train station in Westport, according to the Tier 1 Final Environmental Impact Statement for the FRA’s Preferred Alternative released this month.

“As far as what the aerial structure would look like, we don’t determine that in this recommendation,” said Matthew Lehner, spokesman for NEC Future, the FRA’s vision for the Northeast Corridor. “The design, construction type, aesthetics, etc., would all be determined by state and local leaders if they wanted to move forward with that effort and project. This is often done/called a Tier II study when federal funds are used.”

As such, the FRA has not developed a detailed design for the Preferred Alternative. Rather, the federal agency has developed the following potential construction types for the Preferred Alternative: tunnels, trenches, at-grade, embankments, aerial structures and major bridges.

Old idea, modern engineering

“Aerial structures” aren’t new to railroad construction. Massive wooden trestles were used to span rivers and valleys in the construction of the transcontinental railroad in the 19th century.

The FRA now defines “aerial structures” as bridges and viaducts, which can be used in heavily urbanized areas where at-grade construction isn’t practical. As such, they would be built at river crossings, in wetland areas, through valleys, or crossing over existing roads and highways where vertical grade changes do not permit at-grade construction.

Such construction is being employed as part of California High-Speed Rail. The San Joaquin River Viaduct will comprise a 4,740-foot structure that will span the San Joaquin River and Union Pacific tracks parallel to State Route 99. The viaduct will feature arches representing the northern gateway into Fresno as well as a pergola structure to cross the Union Pacific tracks, according to California High-Speed Rail Authority.

FRA officials note such construction techniques in California but caution against drawing parallels to Connecticut.

Fairfield County

A color-coded conceptual map within the Tier I study shows the potential construction types with yellow denoting tunnels, purple being trenches, blue being at-grade and green designating embankments. “Aerial structures” — designated in red — form a significant stretch of the route from Stamford to Darien.

Local officials have sounded alarm about what such construction might mean for lower Fairfield County where available right-of-way land is scarce and property values are among the highest in the U.S.

“I share the same concerns as Sen. Blumenthal and others as to how that might impact the Norwalk landscape,” said Norwalk Mayor Harry W. Rilling. “And if I’ve been informed correctly, it’s kind of a bypass up to Darien, so we’re being asked to provide the landscape but not reap any of the benefit. So I’m not overly enthused at this point and I certainly will make sure that we make everything we can to protect our city.”

A map provided in the FRA report at www.necfuture.com shows the segment diverging from the existing rail line in Darien and appearing to follow Interstate 95 to Greens Farms.

“However, the NEC Future plan requires the creation of another round of industrial-scale transportation infrastructure in Fairfield County where communities and resources have already suffered the brunt of an expanded I-95,” Mackay said. “Twenty-nine miles of new high-speed-rail routes? It won’t be pretty.”

“Should the FRA continue in its pursuit of its proposed alignment, we will work to ensure that Connecticut exercises every tool at its disposal at the state and federal levels to stop any effort to move forward with this misguided plan,” the elected officials wrote.

Old Lyme, new rails

People in Old Lyme took up the battle against the proposed rail realignment after learning that the plan would bring an “aerial structure” through the center of their historic downtown,

While the FRA appears to have abandoned that construction type in favor of a tunnel, the impacts would be the same, said Gregory Stroud, who founded SECoast, a nonprofit organization that formed in 2016 in response to the proposed high-speed rail plan.

“It’s a choice of poisons. I guess I can’t say which is worse or which is better,” Stroud said. “I can say I don’t believe that the offer of a tunnel is a serious one. We just don’t believe that the FRA is prepared to spend money on a tunnel and we don’t believe it’s feasible. And if it is serious, they should study it before they choose the route.”

SECoast has engaged the Connecticut Preservation Trust in the effort to get the FRA to rethink is plan. The two organizations have asked the FRA to extend the public comment period for the Tier 1 Final Environmental Impact Statement by 60 days. The current deadline for comment is Jan. 31.